434 



GENERAL MORPHOLOGY OF PLANTS 



cottonwoods, and form a large part of the deciduous forest. 

 Aside from the amentiferous trees for timber, shade, and orna- 

 ment, many of the members of these bear nuts which form an 

 important article of food and are the source also of certain kinds 



Fig. 405. 



Cannabis sativa. Hemp brake in operation at Hanover, Penn. With this machine, 

 which breaks the hurds or woody portion of the stalk and separates it from the fiber, four 

 men can clean from 800 to 1200 pounds of hemp fiber in a day. From Fiber Investigations, 

 U. S. Department of Agriculture. 



of oil. Most of these nuts are well known; as walnuts, butter- 

 nuts, pecans, hickory nuts, hazelnuts, filberts, chestnuts, and 

 beechnuts. 



584. The nettle family (Urticaceae) . Hemp. The hemp is 

 cultivated for the fiber and derived from a species (Cannabis 

 sativa) native to central Asia. It has long been cultivated in 

 Europe, and has become naturalized in many countries. The 

 fibers are the nbro-vascular bundles, the other tissues being 

 removed by special processes. It is grown to some extent in the 

 United States for fiber. The hemp is cut with an ordinary mow- 

 ing machine, as shown in g. 403; an elevated horizontal bar 

 bends the stalks forward as they are cut. The hemp is spread 

 on the ground for " retting." Here the soft tissues are disor- 



